PSA after radiation for prostate cancer

The introduction of prostate-specific antigen (PSA) as a reliable tumor marker for prostate cancer brought significant changes in the end points used for outcome reporting after therapy. With regard to a definition of failure after radiation, a consensus was reached in 1996 that took into account the particular issues of an intact prostate after therapy. Over the next several years, the consensus definition issued by the American Society for Therapeutic Radiology and Oncology (ASTRO) was used and studied. Concerns and criticisms were raised. The sensitivity and specificity of this definition vs other proposals has been investigated, and differences in outcome analyzed and compared. Although the ASTRO definition came from analysis of datasets on external-beam radiation and most of the work on this topic has been with this modality, failure definitions for brachytherapy must be explored as well. The concept of a universal definition of failure that might be applied to multiple modalities, including surgery, should also be investigated, at least for comparative study and research purposes.

Dose-volume conundrum for response of prostate cancer to brachytherapy: summary dosimetric measures and their relationship to tumor control probability

PURPOSE

Although it is known that brachytherapy dose distributions are highly heterogeneous, the effect of particular dose distribution patterns on tumor control probability (TCP) is unknown. It is unlikely that clinical results will throw light on the question in the near future, given the long follow-up and detailed dosimetry required for each patient. We used detailed dose distribution data from 50 patients combined with radiobiologic parameters consistent with what is known about TCP curves for prostate cancer to study the changes in TCP that accompany gross dosimetric measures and particular dosing irregularities (e.g., moderate underdosing of large volumes vs. extreme underdosing of small volumes).

METHODS AND MATERIALS

For each of the 50 patients with organ-confined prostate cancer who had undergone 125I prostate implants alone at our clinic, postimplant CT scans were obtained approximately 1 month after implantation. Dose distribution information was obtained from postimplant dosimetry. The percentage of the prostate volume receiving a specified dose was recorded from the respective differential dose-volume histograms in 10-Gy bins. In addition, the percentage of prostate volume underdosed at varying fractions of the prescription dose were determined, as was the minimal prostate dose. The log-normal distributions of the radiobiologic parameters [ln(initial clonogen number), alpha, and alpha/beta] were adjusted so that the predicted population parameters (steepness and location) of the dose-response curves for external beam radiotherapy agreed with the published estimates. The variability in the dose-volume details was increased by scaling the dose distributions by factors ranging from 0.7 to 1.5, thereby simulating, for each of the patients, nine new patients with different total doses but identical relative distributions of the dose over the voxels. Radiobiologic variability between the selected dose distributions was then removed by averaging >50 randomly chosen sets of radiobiologic parameters from the log-normal distributions to estimate the TCP for each of the dose distributions, giving some insight into the TCP variations with conventional dosimetric indexes and different patterns of underdosing.

RESULTS

Using the 450 dose distributions created by expanding the 50-patient data set, the volume of the prostate that was extremely underdosed (between 50% and 70% of the prescription dose) was related to the volume that was moderately underdosed (between 80% and 100% of the prescription dose). We found that the individual TCP is greatly dependent on the inhomogeneous dose distribution and the dosimetric indexes, such as the volume of prostate receiving 100% of the prescribed dose (V100) and the maximal dose received by 90% of the prostate volume (D90), which, by themselves, are not always accurate predictors of control probabilities. In a multivariate analysis of the dependence of TCP on these parameters (V100, D90, minimal dose, and moderately and severely underdosed volumes), only D90 and the minimal dose were statistically significant. Generally speaking, however, a lower minimal dose means a lower TCP.

CONCLUSION

The work described here was an hypothesis-generating study. Our results showed that even if the V100 and D90 are nearly identical for 2 patients, there can be (and frequently are) significant differences in the dose distributions in the subvolumes of the prostate. Under simulated dose-response conditions (i.e., with variations in the dose distribution), the D90 and minimal dose significantly affected the TCP but the V100 and the volumes moderately or severely underdosed did not. In general, one must consider the totality of the dose distribution to evaluate the dosimetric quality of a low-dose-rate prostate implant. TCP is not a monotonic function of extreme or moderate underdosing. In some instances, extreme underdosing of relatively small volumes may result in a greater TCP than moderate underdosing of relatively large volumes and vice versa.

Repopulation of moderately well-differentiated and keratinizing GL human squamous cell carcinomas growing in nude mice

PURPOSE

It has been suggested that, reminiscent of the regulated proliferative response of normal squamous epithelium, squamous cell carcinomas that have preserved characteristics of differentiation have a greater repopulation capacity during fractionated irradiation than undifferentiated tumors. The aim of the present study was to investigate repopulation in moderately well-differentiated and keratinizing GL human squamous cell carcinomas in nude mice.

METHODS AND MATERIALS

GL human squamous cell carcinomas were transplanted s.c. into the right hind leg of NMRI nu/nu mice. Irradiation was performed with 5.4 Gy fractions under clamp hypoxia or with 2 Gy fractions under ambient conditions. Six, 12, or 18 fractions were given daily, every second day, or every third day. Graded top-up doses were applied under clamp hypoxia to determine the tumor control dose 50% (TCD(50)). A total of 20 TCD(50) assays were performed and analyzed using maximum-likelihood techniques.

RESULTS

With an increasing number of daily 5.4 Gy fractions under clamp hypoxia, the top-up TCD(50) values decreased significantly from 50.9 Gy (95% CI: 47, 54) after single doses to 0 Gy after 18 fractions. For the same number of fractions, the top-up TCD(50) increased with increasing overall treatment time. The results are consistent with a constant repopulation rate with a clonogenic doubling time (T(clon)) of 12.7 days (8.6, 16.8). Under ambient blood flow, the top-up TCD(50)s for daily 2 Gy fractions decreased significantly, but were less pronounced than for 5.4 Gy fractions under clamp hypoxia. For a given number of fractions under ambient conditions, the top-up TCD(50)s did not increase significantly with overall treatment time, except for irradiation with 12 fractions in 36 days compared to 12 and 24 days. The T(clon) value from these data was 24.0 days (11.6, 36.4).

CONCLUSION

Our data demonstrate a slow but significant rate of repopulation of clonogenic tumor cells during fractionated irradiation of GL human squamous cell carcinomas under clamp hypoxia without indication of a change of the repopulation rate during treatment. Less pronounced repopulation was observed for irradiation under ambient conditions, which might be explained by preferential survival of hypoxic and therefore nonproliferating cells. Taken together with our previous studies on poorly differentiated FaDu tumors (Petersen et al., IJROBP 2001;51:483-493), the results support important heterogeneity of kinetics and mechanisms of repopulation, in particular of the influence of the oxygenation status of surviving clonogenic cells on the repopulation rate during fractionated irradiation, in different experimental squamous cell carcinoma.

Long-term multi-institutional analysis of stage T1–T2 prostate cancer treated with radiotherapy in the PSA era

PURPOSE

To report the long-term outcome for patients with Stage T1-T2 adenocarcinoma of the prostate definitively irradiated in the prostate-specific antigen (PSA) era.

METHODS AND MATERIALS

Nine institutions combined data on 4839 patients with Stage T1b, T1c, and T2 adenocarcinoma of the prostate who had a pretreatment PSA level and had received >or=60 Gy as definitive external beam radiotherapy. No patient had hormonal therapy before treatment failure. The median follow-up was 6.3 years. The end point for outcome analysis was PSA disease-free survival at 5 and 8 years after therapy using the American Society for Therapeutic Radiology and Oncology (ASTRO) failure definition.

RESULTS

The PSA disease-free survival rate for the entire group of patients was 59% at 5 years and 53% at 8 years after treatment. For patients who had received >or=70 Gy, these percentages were 61% and 55%. Of the 4839 patients, 1582 had failure by the PSA criteria, 416 had local failure, and 329 had distant failure. The greatest risk of failure was at 1.5-3.5 years after treatment. The failure rate was 3.5-4.5% annually after 5 years, except in patients with Gleason score 8-10 tumors for whom it was 6%. In multivariate analysis for biochemical failure, pretreatment PSA, Gleason score, radiation dose, tumor stage, and treatment year were all significant prognostic factors. The length of follow-up and the effect of backdating as required by the ASTRO failure definition also significantly affected the outcome results. Dose effects were most significant in the intermediate-risk group and to a lesser degree in the high-risk group. No dose effect was seen at 70 or 72 Gy in the low-risk group.

CONCLUSION

As follow-up lengthens and outcome data accumulate in the PSA era, we continue to evaluate the efficacy and durability of radiotherapy as definitive therapy for early-stage prostate cancer. Similar studies with higher doses and more contemporary techniques will be necessary to explore more fully the potential of this therapeutic modality.

The addition of continuous infusion 5-FU to preoperative radiation therapy increases tumor response, leading to increased sphincter preservation in locally advanced rectal cancer

PURPOSE

To compare the outcome from preoperative chemoradiation (CXRT) and from radiation therapy (RT) in the treatment of rectal cancer in two large, single-institutional experiences.

PATIENTS AND METHODS

Between 1978 and 1995, 403 patients with localized, nonmetastatic, clinically staged T3 or T4 rectal cancer patients were treated with preoperative RT alone at two institutions. Patients at institution 1 (n = 207) were treated with pelvic CXRT exclusively, and patients at institution 2 were treated (except for 8 given CXRT) with pelvic RT alone (n = 196). In addition, a third group (n = 61) was treated with CXRT at institution 2 between 1998 and 2000 after a policy change. Both institutions delivered 45 Gy in five fractions as a standard dose, but institution 2 used 20 Gy in five fractions in selected cases (n = 26). At both institutions, concurrent chemotherapy consisted of a continuous infusion of 5-fluorouracil (5-FU) at a dosage of 1500 mg/m(2)/week. The end points were response, sphincter preservation (SP), relapse-free survival (RFS), pelvic disease control (PC), and overall survival (OS).

RESULTS

Median follow-up was 63 months for all living patients at institution 1 and in the primary group of institution 2. Multivariate analysis of the patients in these groups showed that the use of concurrent chemotherapy improved tumor response (T-stage downstaging, 62% vs. 42%, p = 0.001, and pathologic complete response, 23% vs. 5% p < 0.0001), but did not significantly improve LC, RFS, or OS. Follow-up for the secondary group at institution 2 was insufficient to allow the analysis of these endpoints. In the subset of patients receiving 45 Gy who had rectal tumors < or /=6 cm from the anal verge (institution 1: n = 132; institution 2 primary: n = 79; institution 2 secondary: n = 33), there was a significant improvement in SP with the use of concurrent chemotherapy (39% at institution 1 compared with 13% in the primary group at institution 2, p < 0.0001). A logistic regression analysis of clinical prognostic factors indicated that the use of concurrent chemotherapy independently influenced SP in these low tumors (p = 0.002). This finding was supported by a 36% SP rate in the secondary group at institution 2. Thus SP increased after the addition of chemotherapy at institution 2.

CONCLUSIONS

The use of concurrent 5-FU with preoperative radiation therapy for T3 and T4 rectal cancer independently increases tumor response and may contribute to increased SP in patients with low rectal cancer.

Radiation for prostate cancer: use of biochemical failure as an endpoint following radiotherapy

The introduction of prostate-specific antigen (PSA) as a reliable tumor marker for prostate cancer brought significant changes in endpoints after therapy and in outcome reporting. Over the last 15 years we have collected follow-up information in this new era and struggled with failure definitions using this new tool. Parameters for failure after radiation were especially controversial due to the fact that, unlike surgery, a variable amount of normal prostate function and PSA production remained. In 1996, the ASTRO Consensus Conference established a PSA failure definition based on the available information at the time. It was commonly used for outcome reporting subsequently although criticisms have been voiced and alternate definitions proposed. A recently assembled multi-institutional database was used both for long-term outcome reporting with external beam radiation and to test various other failure definitions. A summary of these results and the associated issues are presented here.

Indium-111-capromab pendetide radioimmunoscintigraphy and prognosis for durable biochemical response to salvage radiation therapy in men after failed prostatectomy

PURPOSE

We evaluated the prognostic significance of indium-111 (111In)-capromab pendetide imaging for patients with prostate cancer who underwent salvage radiotherapy (RT) for recurrent disease after prostatectomy.

PATIENTS AND METHODS

Records were reviewed for all men who underwent 111In-capromab pendetide imaging at a single institution from February 1997 through December 1999. We identified 30 eligible men who were radiographically negative for metastatic disease, who had increasing serum prostate-specific antigen (PSA) after primary radical prostatectomy, and who received salvage RT. Clinical interpretations of indium monoclonal antibody (In-mab) scan results were compared with postsalvage RT PSA response.

RESULTS

Using an American Society of Therapeutic Radiation and Oncology definition of PSA failure, in men with a positive scan in at least one location (n = 14), the cumulative 2-year PSA control after salvage RT was 0.38 +/- 0.13 (+/- SE) compared with 0.31 +/- 0.13 for men with a normal antibody scan in and outside the prostate fossa (n = 15; proportional hazard ratio [PHR] = 1.32; 95% confidence interval [CI], 0.52 to 3.36). For men with a positive antibody scan limited to the prostate fossa (n = 9), PSA control at 2 years was 0.13 +/- 0.12 (PHR 1.77; 95% CI, 0.65 to 4.85). The 2-year probability of PSA control after salvage RT for men with positive scan results outside the prostate bed irrespective of In-mab findings in the prostate fossa (n = 5) was 0.60 +/- 0.22 (PHR 0.81; 95% CI, 0.17 to 3.78).

CONCLUSION

In contrast to previous reports, for patients with postprostatectomy biochemical relapse who received salvage RT, presalvage RT In-mab scan findings outside the prostate fossa were not predictive of biochemical control after RT.

Response to preoperative chemoradiation increases the use of sphincter-preserving surgery in patients with locally advanced low rectal carcinoma

BACKGROUND

Although controversial, some believe that preoperative chemoradiation increases the use of sphincter-preserving surgery in low rectal carcinoma patients. This article investigates the relationship between objective tumor response and sphincter preservation in low rectal carcinoma patients.

METHODS

The authors reviewed the records of 238 patients with T3 or T4 low rectal carcinoma (< or = 6 cm from the anal verge) who underwent preoperative pelvic chemoradiation (45 Gy/25 fractions/5 weeks, n = 182 or 52.5 Gy/30 fractions/5 weeks, n = 56 with continuous infusion 5-fluorouracil at 300 mg/m(2), Monday to Friday) followed by mesorectal (n = 223) or local excision (n = 15). A logistic regression analysis was used to analyze the influence of objective tumor response (defined as complete clinical response) and other prognostic factors on sphincter preservation. Because degrees of partial response could not be objectively defined retrospectively, the influence of partial response on sphincter preservation could not be evaluated.

RESULTS

Overall, 49% of patients (117 of 238) had sphincter-preserving surgery. The clinical complete response rate was 47%. Independent predictors of sphincter preservation included the year of surgery, tumor distance from the anal verge, circumferential tumor involvement, and response to chemoradiation. The sphincter preservation rate increased over the period of the study (from 28% [December 1989 to December 1992] to 44% [January 1993 to December 1996] to 67% [January 1997 to December 2000]). The difference in the rates of sphincter preservation according to response was most striking among patients with tumors 3 cm or less from the anal verge (44% vs. 22%, P = 0.01). The pelvic disease recurrence rate among patients undergoing sphincter-preserving surgery has been less than 10% since January 1993 and was not statistically different between the groups treated from January 1993 to December 1996 and from January 1997 to December 2000.

CONCLUSIONS

There has been an increase in the use of sphincter-preserving surgery without an increase in pelvic disease recurrence over the past decade. Although not necessary for sphincter preservation, clinical response to preoperative chemoradiation independently contributed to sphincter-preserving surgery, particularly in patients with low rectal tumors.

Immunohistochemically detected p53 mutations in epithelial tumors and results of treatment with chemotherapy and radiotherapy. A treatment-specific overview of the clinical data

BACKGROUND

The aim was to ascertain whether many hundreds of clinical reports over the last decade are consistent with the prediction of a poorer outcome in cancer patients with p53 abnormalities treated with cytotoxic drugs and radiation.

MATERIAL AND METHOD

There are 301 studies on the influence of p53 overexpression published through summer 2000, in which chemotherapy or radiotherapy was used alone or in combination with surgery. From 45 reports meeting stringent selection rules, comparison groups are identified in whom the same measure of outcome was reported for the same treatment applied to the same tumor, with results corrected for important prognostic factors. Metaanalysis techniques are then applied to the comparison groups. Attention was limited to reports using immunohistochemical techniques, to form comparison groups of sufficient size.

RESULTS

Four comparison groups were identified by treatment and endpoint: 1) Stage I-III breast cancer (surgery and chemotherapy, disease-free survival, seven studies); 2) stage I-III breast cancer (surgery and chemotherapy, overall survival, six studies); 3) stage II-IV head and neck cancer (radiotherapy and chemotherapy, overall survival, five studies); 4) FIGO I-IV ovarian cancer (surgery and chemotherapy, overall survival, six studies). In the breast (disease-free survival) and ovarian (overall survival) comparison groups, the hazard ratio for a deleterious effect of p53 overexpression was significant or marginally significant, depending on assumed ranges for unreported hazard ratios in non-significant studies.

CONCLUSIONS

Despite the many caveats related to metaanalysis applied to retrospective data, high variability of immunohistochemical technique, etc., a nearly significant negative effect of p53 overexpression on outcome of treatment with cytotoxic drugs and radiation emerges in the few studies where heterogeneity can be sufficiently reduced or accounted for.

Pathologic tumor size and lymph node status predict for different rates of locoregional recurrence after mastectomy for breast cancer patients treated with neoadjuvant versus adjuvant chemotherapy

PURPOSE

To compare the pathologic factors associated with postmastectomy locoregional recurrence (LRR) in breast cancer patients not receiving radiation who were treated with neoadjuvant chemotherapy (NEO) vs. adjuvant chemotherapy (ADJ).

METHODS AND MATERIALS

We retrospectively analyzed the rates of LRR of subsets of women treated in prospective trials who underwent mastectomy and received chemotherapy but not radiation. These trials were designed to answer chemotherapy questions. There were 150 patients in the NEO group and 1031 patients in the ADJ group. In the NEO group, 55% had clinical Stage IIIA or higher vs. 9% in the ADJ group (p <0.001, chi-square test).

RESULTS

Despite the more advanced clinical stage in the NEO group, the pathologic size of the primary tumor and the number of positive lymph nodes (+LNs) were significantly less in the NEO group than in the ADJ group (p <0.001 for both comparisons). However, the 5-year actuarial LRR rate was 27% for the NEO group vs. 15% for the ADJ group (p = 0.001, log-rank). The 5-year risk for LRR was higher in the NEO patients for all pathologic tumor sizes: 0-2 cm (18% vs. 8%, p = 0.011), 2.1-5 cm (36% vs. 15%, p <0.001), and >5 cm (46% vs. 28%, p = 0.028). The risk of LRR by the number of +LNs was similar in the NEO and ADJ groups, except for the subset of patients with > or =4 +LNs (53% vs. 23%, p <0.001). The rates of LRR in the patients with primary tumors measuring < or =2.0 cm and 1-3 +LNs were similar in both groups. However, for the patients with a pathologic tumor size of 2.1-5.0 cm and 1-3 +LNs, the LRR was higher in the NEO group than in the ADJ group (30% vs. 15%, p = 0.016). Most failures in this NEO subgroup had clinical Stage III disease. In a subset of NEO and ADJ patients matched for clinical stage, no significant differences were found in the rates of LRR according to primary tumor size and number of +LNs when these variables were analyzed independently. Again, however, differences were found in the subgroup of patients with tumors pathologically measuring 2.1-5.0 cm with 1-3 +LNs (32% NEO vs. 8% ADJ, p = 0.030).

CONCLUSION

The rates of postmastectomy LRR for any pathologic tumor size are higher for patients treated with initial chemotherapy than for patients treated with initial surgery. Radiotherapy should be offered to all patients with > or =4 +LNs, tumor size >5 cm, or clinical Stage IIIA or greater disease, regardless of whether they receive neoadjuvant or postoperative chemotherapy. The information assessing LRR rates in patients with clinical Stage II disease who receive neoadjuvant chemotherapy, particularly if 1-3 lymph nodes remain pathologically involved, is insufficient to determine whether these patients should receive radiotherapy.

Randomized phase III study of chemoradiation with or without amifostine for patients with favorable performance status inoperable stage II-III non-small cell lung cancer: preliminary results

A prospective randomized study was conducted to determine whether amifostine (Ethyol) reduces the rate of severe esophagitis and hematologic and pulmonary toxicity associated with chemoradiation or improves control of non-small cell lung cancer (NSCLC). Sixty patients with inoperable stage II or III NSCLC were treated with concurrent chemoradiotherapy. Both groups received thoracic radiation therapy (TRT) with 1.2 Gy/fraction, 2 fraction per day, 5 days per week for a total dose 69.6 Gy. All patients received oral etoposide (VP-16), 50 mg Bid, 30 minutes before TRT beginning day 1 for 10 days, repeated on day 29, and cisplatin 50 mg/m(2) intravenously on days 1, 8, 29, and 36. Patients in the study group received amifostine, 500 mg intravenously, twice weekly before chemoradiation (arm 1); patients in the control group received chemoradiation without amifostine (arm 2). Patient and tumor characteristics were distributed equally in both groups. Of the 60 patients enrolled, 53 were evaluable (27 in arm 1, 26 in arm 2) with a median follow-up of 6 months. Median survival times were 26 months for arm 1 and 15 months for arm 2, not statistically significantly different. Morphine intake to reduce severe esophagitis was significantly lower in arm 1 (2 of 27, 7.4%) than arm 2 (8 of 26, 31%; P =.03). Acute pneumonitis was significantly lower in arm 1 (1 of 27, 3.7%) than in arm 2 (6 of 26, 23%; P =.037). Hypotension (20 mm Hg decrease from baseline blood pressure) was significantly more frequent in arm 1 (19 of 27, 70%) than arm 2 (1 of 26, 3.8%; P =.0001). Only 1 patient discontinued treatment because of hypotension. These preliminary results showed that amifostine significantly reduced acute severe esophagitis and pneumonitis. Further observation is required to assess long-term efficacy.

Direct evidence that prostate tumors show high sensitivity to fractionation (low alpha/beta ratio), similar to late-responding normal tissue

PURPOSE

A direct approach to the question of whether prostate tumors have an atypically high sensitivity to fractionation (low alpha/beta ratio), more typical of the surrounding late-responding normal tissue.

METHODS AND MATERIALS

Earlier estimates of alpha/beta for prostate cancer have relied on comparing results from external beam radiotherapy (EBRT) and brachytherapy, an approach with significant pitfalls due to the many differences between the treatments. To circumvent this, we analyze recent data from a single EBRT + high-dose-rate (HDR) brachytherapy protocol, in which the brachytherapy was given in either 2 or 3 implants, and at various doses. For the analysis, standard models of tumor cure based on Poisson statistics were used in conjunction with the linear-quadratic formalism. Biochemical control at 3 years was the clinical endpoint. Patients were matched between the 3 HDR vs. 2 HDR implants by clinical stage, pretreatment prostate-specific antigen (PSA), Gleason score, length of follow-up, and age.

RESULTS

The estimated value of alpha/beta from the current analysis of 1.2 Gy (95% CI: 0.03, 4.1 Gy) is consistent with previous estimates for prostate tumor control. This alpha/beta value is considerably less than typical values for tumors (> or =8 Gy), and more comparable to values in surrounding late-responding normal tissues.

CONCLUSIONS

This analysis provides strong supporting evidence that alpha/beta values for prostate tumor control are atypically low, as indicated by previous analyses and radiobiological considerations. If true, hypofractionation or HDR regimens for prostate radiotherapy (with appropriate doses) should produce tumor control and late sequelae that are at least as good or even better than currently achieved, with the added possibility that early sequelae may be reduced.

Biased methods for estimating local and distant failure rates in breast carcinoma and a "commonsense" approach

BACKGROUND

Several methods are used to estimate risks of local and distant failure after treatment of breast carcinoma. The authors' purpose was to present a physician-friendly description of the potential bias in these methods, and to suggest an improvement.

METHODS

The cumulative incidence based on first event (cumulative incidence [CI]) and Kaplan-Meier method based on first (KM[1st]) or all (KM[any]) events, are applied to a database comprising 2521 women treated for breast carcinoma at the same institution and observed for more than 20 years. The authors relate these estimates to the region containing all possible estimates of failure rate. This region contains the "true" risk (net risk, or risk that would be observed in the absence of competing risks) of local or distant failure.

RESULTS

The CI estimate is the lowest possible estimate of the true failure rate. Under certain "commonsense" assumptions, the CI estimate is below the lowest possible estimate of risk of failure. The KM(1st) estimate is higher than the CI estimate and lower than the KM(any) estimate. Under the same commonsense assumptions, the KM(1st) method also underestimates the true failure rate.

CONCLUSIONS

Methods based on time to first event such as CI and KM(1st) underestimate the true risk. In the design of clinical trials, consideration should be given to longer follow-up and the KM(any) method of analyzing results because it provides a less biased estimate.

Repopulation of FaDu human squamous cell carcinoma during fractionated radiotherapy correlates with reoxygenation

PURPOSE

FaDu human squamous cell carcinoma (FaDu-hSCC) showed a clear-cut time factor during fractionated radiotherapy (RT) under ambient blood flow. It remained unclear whether this is caused solely by proliferation or if radioresistance resulting from increasing hypoxia contributed to this phenomenon. To address this question, repopulation of clonogenic FaDu cells during fractionated RT under clamp hypoxia was determined by local tumor control assays, and compared to the results after irradiation with the same regimen under ambient blood flow.

METHODS AND MATERIALS

FaDu-hSCC was transplanted into the right hind leg of NMRI nu/nu mice. In the first set of experiments, irradiation was performed under clamp hypoxia. After increasing numbers of 3 Gy fractions (time intervals 24 h or 48 h), graded top-up doses were given to determine the TCD(50) (dose required to control 50% of the tumors). In the second set of experiments, all 3 Gy fractions were applied under ambient conditions, but as in the previous experiments the graded top-up doses were given under clamp hypoxia. A total of 26 TCD(50) assays were performed and analyzed using maximum likelihood techniques.

RESULTS

With increasing numbers of daily fractions, the top-up TCD(50) under clamp hypoxia decreased from 39.4 Gy [95% CI 36, 42] after single dose to 19.8 Gy [15, 24] after 18 fractions in 18 days and to 37.8 Gy [31, 44] after 18 fractions in 36 days. The results were consistent with biphasic repopulation, with a switch to rapid repopulation after about 22 days [13, 30]. The clonogen doubling time (T(clon)) decreased from 9.8 days [0, 21] in the beginning of RT to 3.4 days after 22 days. Under ambient blood flow the top-up TCD(50) decreased from 37.6 Gy [34, 40] after single dose irradiation to 0 Gy [0, 1] after 18 fractions in 18 days and 22.4 Gy [18, 27] after 18 fractions in 36 days. Similar to results from irradiations under clamp hypoxia, the ambient data were consistent with a biphasic course of clonogen inactivation. Comparison of both data sets revealed significant reoxygenation after 12 fractions.

CONCLUSIONS

Our data are most consistent with a biphasic course of clonogen repopulation during fractionated RT of FaDu-hSCC under clamp hypoxia with a switch in T(clon) after about 22 days of treatment ("dog-leg"). A similar biphasic course of cell repopulation was observed under ambient conditions. The temporal coincidence between repopulation and reoxygenation suggests that the latter might be the stimulus for proliferation in FaDu tumors.

The proliferative response of mouse jejunal crypt cells to radiation-induced cell depletion is not mediated exclusively by transforming growth factor alpha

Several lines of correlative evidence link transforming growth factor alpha (Tgfa, also known as TGF-alpha) to proliferative activity in jejunal crypt cells. It is therefore tempting to hypothesize that, as a ligand of the epidermal growth factor, it mediates the compensatory proliferative burst in the crypts after radiation-induced cell killing. We have tested this hypothesis by comparing the repopulation response of wild-type and Tgfa-null mice, using the microcolony assay. Mice were exposed whole-body to (137)Cs gamma rays at a dose of approximately 1.6 Gy/min. Single doses and equal doses separated by 4 and 54 h were given. The rightward shift of the dose-response curves for 54 h was identical for wild-type and Tgfa-null mice, and there was no indication of a difference in radiosensitivity. This result indicates that Tgfa is not an essential component of the proliferative response of tissue to radiation-induced cell killing.

The results of colorectal cancer treatment by p53 status: treatment-specific overview

PURPOSE

Both negative and positive influences of mutant p53 on treatment outcome have been reported, and we present here a meta-analysis of published studies where outcome was reported for defined treatment groups.

METHODS

We identified articles on the effect of p53 status by treatment modality, excluding those not stratified by method of treatment. A common hazard ratio was estimated from studies that reported a multivariate analysis. We also estimated the numbers of patients expressing the endpoint at the mean or median follow-up time and calculated a pooled odds ratio.

RESULTS

Twenty-eight articles were evaluable (23 using immunohistochemistry to detect overexpression of p53 and 8 using DNA sequencing), for a total of 4,416 patients. For patients treated with surgery only, the immunohistochemistry studies showed a significant influence of p53 status on disease-free survival and a marginally significant influence on overall survival. In the studies using DNA sequencing, by contrast, there was a significant influence of p53 mutations on overall survival, but not disease-free survival. For patients treated with surgery and radiotherapy, the influence of p53 status on disease-free survival was either insignificant or marginally significant, depending on test used; there was no influence on overall survival.

CONCLUSIONS

Although this pooled analysis of published studies where treatment was accounted for shows that there is a borderline significant hazard associated with p53 overexpression or mutation vs. p53 wild-type, it is unlikely that p53 can be applied in a routine clinical setting alongside factors such as T stage, nodal status, and residual tumor, whose prognostic value is much stronger.

The translational research chain: is it delivering the goods?

PURPOSE

To address whether the translational research chain has influenced clinical practice in radiation oncology.

METHODS AND MATERIALS

Merits and limitations of the various steps of the translational chain, i.e., in vitro studies, animal experiments, biomathematical modeling, Phase I and II trials, and randomized Phase III trials are briefly reviewed. The process and value of translational research in radiation oncology are addressed using dose fractionation and the time factor in tumors as examples.

RESULTS

The examples show that translational research may indeed change clinical practice in radiation oncology. However, it takes several decades and considerable efforts to define and test new strategies. The "translational process" is by no means unidirectional but a continuing multiway dialog among basic scientists, applied scientists, clinical scientists, and clinical oncologists.

CONCLUSION

Translational research works in radiation oncology, and it is difficult to conceive a better alternative for future improvement of therapy. The slow speed of the translational process indicates that there is a need for improving the various steps of the translational network and the interaction as a whole. Massive investments in one part of the network are likely to be at least partly wasted unless the other links are strengthened as well.

The challenge of p53 as prognostic and predictive factor in Hodgkin's or non-Hodgkin's lymphoma

The results of individual studies examining the role of p53 as a predictive and prognostic factor in lymphoid malignancies have varied considerably. In order to summarize the available data on the overexpression or mutation of p53 in Hodgkin's and non-Hodgkin's lymphoma, a systematic literature review was performed. Twenty-four studies met the eligibility criteria. With respect to non-Hodgkin's lymphoma, most studies seem to support the hypothesis that patients whose tumors contain wild-type p53 respond better to treatment and have increased survival rates. If true, the implication may be that patients with p53 mutated tumors could be selected for non-standard treatment. With respect to Hodgkin's lymphoma, comparable associations were rarely reported. However, techniques for assessing the inactivation of p53 varied widely. Furthermore, in most instances, the study design and/or statistical methods did not allow sufficient analyses of the influence of confounding factors such as histologic type, stage, first-line and salvage treatment, etc. Therefore, it remains unclear whether the apparent influence of p53 status on outcome in non-Hodgkin's lymphoma is independent of established parameters such as stage, performance status, etc. Further studies involving large numbers of specimens derived from patients treated in clinical trials with identical regimens, follow-up and salvage strategies are needed. These studies should also be stratified according to histologic subtypes.

Local-regional control in breast cancer patients with a possible genetic predisposition

PURPOSE

Local control rates for breast cancer in genetically predisposed women are poorly defined. Because such a small percentage of breast cancer patients have proven germline mutations, surrogates, such as a family history for breast cancer, have been used to examine this issue. The purpose of this study was to evaluate local-regional control following breast conservation therapy (BCT) in patients with bilateral breast cancer and a breast cancer family history.

METHODS AND MATERIALS

We retrospectively reviewed records of all 58 patients with bilateral breast cancer and a breast cancer family history treated in our institution between 1959 and 1998. The primary surgical treatment was a breast-conserving procedure in 55 of the 116 breast cancer cases and a mastectomy in 61. The median follow-up was 68 months for the BCT patients and 57 months for the mastectomy-treated patients.

RESULTS

Eight local-regional recurrences occurred in the 55 cases treated with BCT, resulting in 5- and 10-year actuarial local-regional control rates of 86% and 76%, respectively. In the nine cases that did not receive radiation as a component of their BCT, four developed local-regional recurrences (5- and 10-year local-regional control rates of BCT without radiation: 49% and 49%). The 5- and 10-year actuarial local-regional control rates for the 46 cases treated with BCT and radiation were 94% and 83%, respectively. In these cases, there were two late local recurrences, developing at 8 years and 9 years, respectively. A log rank comparison of radiation versus no radiation actuarial data was significant at p = 0.009. In the cases treated with BCT, a multivariate analysis of radiation use, patient age, degree of family history, margin status, and stage revealed that only the use of radiation was associated with improved local control (Cox regression analysis p = 0.021). The 10-year actuarial rates of local-regional control following mastectomy with and without radiation were 91% and 89%, respectively.

CONCLUSIONS

Patients with a possible genetic predisposition to breast cancer had low 5-year rates of local recurrence when treated with breast conserving surgery and radiation, but the local failure rate exceeded 50% when radiation was omitted. Our data are consistent with the hypothesis that patients with an underlying genetic predisposition develop cancers with radiosensitive phenotypes.

Locoregional recurrence patterns after mastectomy and doxorubicin-based chemotherapy: implications for postoperative irradiation

PURPOSE

The objective of this study was to determine locoregional recurrence (LRR) patterns after mastectomy and doxorubicin-based chemotherapy to define subgroups of patients who might benefit from adjuvant irradiation.

PATIENTS AND METHODS

A total of 1,031 patients were treated with mastectomy and doxorubicin-based chemotherapy without irradiation on five prospective trials. Median follow-up time was 116 months. Rates of isolated and total LRR (+/- distant metastasis) were calculated by Kaplan-Meier analysis.

RESULTS

The 10-year actuarial rates of isolated LRR were 4%, 10%, 21%, and 22% for patients with zero, one to three, four to nine, or >/= 10 involved nodes, respectively (P <.0001). Chest wall (68%) and supraclavicular nodes (41%) were the most common sites of LRR. T stage (P <.001), tumor size (P <.001), and >/= 2-mm extranodal extension (P <.001) were also predictive of LRR. Separate analysis was performed for patients with T1 or T2 primary disease and one to three involved nodes (n = 404). Those with fewer than 10 nodes examined were at increased risk of LRR compared with those with >/= 10 nodes examined (24% v 11%; P =.02). Patients with tumor size greater than 4.0 cm or extranodal extension >/= 2 mm experienced rates of isolated LRR in excess of 20%. Each of these factors continued to significantly predict for LRR in multivariate analysis by Cox logistic regression.

CONCLUSION

Patients with tumors >/= 4 cm or at least four involved nodes experience LRR rates in excess of 20% and should be offered adjuvant irradiation. Additionally, patients with one to three involved nodes and large tumors, extranodal extension >/= 2 mm, or inadequate axillary dissections experience high rates of LRR and may benefit from postmastectomy irradiation.