Fast neutron irradiation of metastatic cervical adenopathy: the results of a randomized RTOG study

Radiation techniques in neuro-oncology

Radiation therapy plays a critical role in the management of tumors of the brain. A variety of radiotherapy techniques have been used to treat these tumors. This review describes both classic and more recent and advanced techniques available to manage these tumors. Included is a discussion of standard two- and three-dimensional radiation, as well as intensity-modulated radiotherapy, image-guided radiation therapy, stereotactic radiosurgery, and heavy particles.

Carcinoma of the larynx treated with hypofractionated radiation and hyperbaric oxygen: long-term tumor control and complications

PURPOSE

To evaluate the long-term outcome with respect to local control, survival, and complications in a cohort of patients with locally advanced laryngeal carcinoma treated with hypofractionated radiation and hyperbaric oxygen at 4 atmospheres of pressure (HBO-4).

METHODS AND MATERIALS

Between January 1970 and August 1982, 45 patients with locally advanced carcinoma of the larynx were treated with primary radiation using a unique hypofractionated schedule of 2 fractions of 11 Gy separated by 21 days, with concomitant HBO-4 during each radiotherapy session. To avoid seizures, discomfort and other complications of HBO-4, each session was performed under general anesthesia. All patients had pathologically confirmed squamous cell carcinoma of the glottic (23) or supraglottic larynx (22) and were staged as follows: T2-5, T3-24, T-4-16; N0-26, N1-4, N2-13, N3-1. Patients were treated with opposed lateral wedged fields of 4-6 MV photons, with a median field size of 5.5 x 9.75 to a total median dose of 22.5 Gy.

RESULTS

As of February 1998, follow-up was complete on all but one patient, who relocated to another country after 8 years. Complete clinical responses were observed in 39 (87%) of the cases. The 10-year local control rate for all 45 patients was 58%, and local control for the complete responders was 69%. Three patients underwent laryngectomy for complications and were found to have no pathological evidence of disease in the laryngectomy specimen. The 10-year survival of the overall population was 27%. The 10-year voice preservation rate for the the 39 complete responders was 55%. Acute mucosal and skin reactions were modest and acceptable. Significant late complications occurred in 14 patients consisting of severe fibrosis, necrosis, pharyngeal fistula, with 3 patients requiring laryngectomy for complications. The actuarial rate of severe complications at 5 years was 42%.

CONCLUSIONS

The response rate and long-term tumor control rate obtained with this treatment program were comparable to more protracted radiation schedules with or without systemic chemotherapy. The complication rate was high resulting in an adverse therapeutic ratio. The radiobiologic interpretation of this clinical data, and implications for hypoxia directed therapy, are discussed.

Concurrent platinum-based chemotherapy and hyperfractionated radiotherapy with late intensification in advanced head and neck cancer

PURPOSE

To determine whether a course of hyperfractionated radiation therapy concomitant with escalated radiosensitizing platinum compounds can be administered with acceptable morbidity and achieve a high rate of loco-regional control for Stage III and IV head and neck cancer and whether the patients can be tumor free at the primary site after initial therapy and cured by the additional chemoradiation without radical resection of the primary tumor.

METHODS AND MATERIALS

Patients with Stage III/IV head and neck cancer were treated in this multicenter Phase II Study with 1.8 Gy fraction radiotherapy for 2 weeks, with escalation to 1.2 Gy b.i.d. hyperfractionation to 46.8 Gy. Concomitant continuous infusion cisplantinum (CDDP) 20 mg per meter square on day 1 to 4 and 22 to 25 was given. Reassessment by biopsy of primary and nodes was done. Patients with a complete response continued with hyperfractionated radiotherapy to 75.6 Gy with simultaneous carboplatinum (Carbo), 25 mg per meter square b.i.d. for 12 consecutive treatment days. Patients with residual disease at 46.8 Gy required curative surgery. Seventy-four patients were treated at the three institutions; 20 were Stage III and 54 were Stage IV. All patients had daily mouth care, nutritional, and psychosocial support.

RESULTS

This regime was well tolerated. Eighty-five percent of toxicities were Grade 1 or 2 and there was only one Grade 4 hematologic toxicity. Late toxicities included xerostomia in 25 patients, dysphasia in 18, and mild speech impediment in 11. Biopsies of primary site were done after the first course of treatment in 59 patients. Neck dissections were performed in 35 patients. Forty-four of 59 (75%) primary sites and 16 of 35 (46%) lymph nodes had pathologically complete response (CR). Of the 74 patients, only 12 required surgical resection of the primary site. Thirty-five of the 50 node positive patients had neck dissections, 16 of these were CRs at surgery. At 4 years (median follow-up of 26 months), disease-specific survival is 63%. The actuarial survival for all patients is 51%. Patients with pathological CR after initial treatment have disease specific survival of 73% at 4 years vs. 48% of patients with partial response (PR) only.

CONCLUSION

This study, developed on the basis of radiobiological and cell kinetic precepts, produced results that compare favorably with other reports of management of patients with advanced head and neck cancer. In comparison with our previous study, these results are comparable, not impressively better. The associated morbidity was somewhat worse.

Preoperative thermochemotherapy of oral cancer using magnetic induction hyperthermia (Implant Heating System: IHS)

Eight patients with primary cancer of the oral cavity were preoperatively treated by combined treatment with hyperthermia and chemotherapy. They received two courses of chemotherapy, which included intra-arterial infusion of 100 mg of cisplatin (CDDP) and 25 mg of peplomycin (PEP) via the superficial temporal artery. The patients also received interstitial hyperthermia for 45 min once a week using the Implant Heating System (IHS) with chemotherapy. IHS consists of ferromagnetic implant, induction coil and generator to produce high frequency magnetic field. The ferromagnetic implant is made of Fe-Pt alloy (Fe: 73%, Pt: 27%), and has a Curie temperature of 68 degrees C. As a result, clinical complete response (CR) was observed in seven patients and partial response (PR) in one, and postoperative pathological examination showed no residual tumour cells in any specimen. Combined interstitial hyperthermia by IHS and chemotherapy is thus found to be an effective therapeutic method for treating oral cancers.

Preoperative cisplatin and accelerated hyperfractionated radiation induces high tumor response and control rates in patients with advanced head and neck cancer

BACKGROUND

Preoperative therapy with concurrent cisplatin infusion and accelerated hyperfractionated radiation has the potential to eradicate pools of resistant cells with high-growth fraction that accumulate during standard radiation therapy. Based on preliminary data showing a high complete response rate (necessary for organ preservation) in patients with advanced squamous cell cancer of the head and neck (stages III and IV), we conducted a multi-institutional study using accelerated hyperfractionated radiation to maximize local and regional tumor control without adding toxicity.

PATIENTS AND METHODS

Preoperative radiation was given in 1.8 Gy fractions for 2 weeks followed by 1.2 Gy BID hyperfractionation to 46.7 Gy. Continuous infusion of cisplatin 20 mg/m2 was given on days 1 through 4 and 22 through 25. Patients were initially assessed with panendoscopy and were subsequently reassessed with biopsy of primary site (+/- nodes). Patients with negative primary site biopsy received additional hyperfractionated radiation to 76 Gy with simultaneous carboplatin 25 mg/m2 BID for 12 consecutive days. Patients with residual disease after 47 Gy had resection of primary site and node dissection. Of 69 patients treated, 56 were T3 and T4, and 46 were N1, N2, and N3; 17 patients (25%) were stage III and 50 (72%) were stage IV; in 2 patients (3%) the stage was unknown.

RESULTS

Treatment was well tolerated with no grade IV toxicities, but there were 13 patients with grade III toxicities (mucositis, dysphagia, or hematological toxicity). Biopsy specimens were taken from 84% of the patients, and 81% of the primary sites showed pathologic complete response and 49% of the lymph nodes showed a pathologic complete response. Thirty-four patients underwent curative surgery. Eleven required resection of the primary and 23 required neck dissection only. At 2 years (median followup 12 months), 44 of 69 patients (64%) have no evidence of disease, 9 are dead of disease, 9 are dead of other causes, and 6 are alive with disease. Surgical toxicities were minimal and primarily limited to fibrosis in 12 patients, edema in 8 patients, tracheoesophageal fistula in 1 patient, and delayed wound healing in 1 patient. Late toxicities included xerostomia in 22 patients, dysphagia in 17, and speech impairment in 9.

CONCLUSIONS

Preoperative concurrent radiotherapy and chemotherapy provides a high level of organ preservation and local and regional control because of the high complete response rate at the primary site. A planned neck dissection with minimal morbidity ensures local/regional control, as well as providing definitive staging information. A randomized evaluation is suggested for this program.

An evaluation of the results of neutron therapy trials

Twenty-five randomised clinical trials have been completed which have investigated the value of fast neutron therapy. The results of these trials are reviewed in terms of the reported rates of local tumour control and late morbidity. The trials have included patients with cancers of the head and neck region, brain, lung, pancreas, cervix, bladder and rectum. None has demonstrated neutrons to be advantageous compared with photons. Two trials of locally advanced prostate cancer have given conflicting results. A trial of mixed schedule therapy has demonstrated improved local tumour control and survival. A trial of neutrons alone for similar stage disease has not shown any therapeutic advantages. It is still claimed that salivary gland tumours may be more effectively treated by neutrons but the clinical trial results are not definitive. Late morbidity after neutron therapy is a persistent cause for concern and often has been unacceptably high. There is no convincing evidence that fast neutrons are either as safe or as effective in cancer control as photon therapy.

Preoperative combined chemotherapy and radiation therapy plus radical surgery in advanced head and neck cancer. Five-year results with impressive complete response rates and high survival

Radiation therapy combined with cisplatin as a chemoradiation sensitizer (CT/RT) has been reported to enhance tumor response in squamous cell carcinoma of the head and neck. In the present study, CT/RT was used preoperatively in advanced Stage III and IV head and neck cancer. Fifty-three patients were entered prospectively into a Phase II study. Treatment consisted of 4500 cGy of radiation therapy in 5 weeks combined with cisplatin 20 mg/m2 for 4 days during weeks 1 and 4 of radiation therapy. This was followed 4 to 8 weeks later by curative surgery. Pretherapy dental care; long-term nutritional support; individualized skin, mouth, and wound care; and continuous interdisciplinary communication were integral parts of this regimen. In four patients, CT/RT toxicity was seen (8%); three episodes of skin reaction or stomatitis and three episodes of leukopenia (less than 2500/microliters), causing a delay in CT/RT treatment in one patient. Three patients died of other causes during the preoperative interval, without clinical evidence of toxicity. Fifty patients (94%) had a complete (CR) or partial response (PR) to CT/RT. Clinical CR was seen in 38 of 51 (75%) primary tumors and 21 of 27 (78%) cervical nodes. Forty-one patients (77%) underwent curative surgery. In 27 of 32 (84%) resected CR primary tumors and 16 of 18 (89%) CR metastatic nodes, the surgical specimen was microscopically free of tumor. Postoperative morbidity was 32%. Five patients (12%) required additional surgery for their complications. Perioperative mortality was 5%. Five patients had tumor recurrence: three postoperatively after clinical PR to CT/RT and two in clinical CR patients who refused further treatment after CT/RT, then had a recurrence and were salvaged surgically. No patient with a CR in both the tumor and nodes who underwent surgery had a tumor recurrence. With a follow-up of 8 years (median, 40 months), the median survival for all patients was 45 months. The 5-year actuarial survival rate was 43% for all patients and 55% for patients who had CT/RT and surgery. This multimodality treatment of advanced head and neck cancer has low toxicity and impressive survival. It renders a significant number of patients tumor-free before surgery. These patients may be candidates for additional study triaging additional CT/RT for complete CR only and surgery for PR and biopsy-proved residual disease.

Neutron therapy in Saudi Arabia: an overview and results of dose searching study in head and neck cancer

The King Faisal Specialist Hospital and Research Centre is the only center in the Middle East that incorporates a neutron therapy facility. The neutron beam is produced by a cyclotron, which produces a beam by either a (d(15)+Be) or (p(26)+Be) reaction. The beam from the proton reaction is selected for therapy because of its superior physical characteristics. These were verified by an intercomparison conducted by the European Organization for Research on Treatment of Cancer (EORTC) Heavy Particle Therapy Group. Full beam data are presented. The first study in the neutron therapy Program is on the treatment of squamous cancers of the head and neck. This consists of two parts. Part I is a dose searching phase and Part II is a comparison of our current photon treatment versus neutrons using the neutron dose selected by Part I of the study. Results of the dose searching phase (Part I) are presented.

The effect of local-regional control on distant metastatic dissemination in carcinoma of the head and neck: results of an analysis from the RTOG head and neck database

A retrospective analysis of the effect of local control on the development of distant metastases was performed in 2648 patients with carcinoma of the head and neck selected from the RTOG database. The 5-year time-adjusted incidence of distant metastases was 21% for patients who were in local-regional control at 6 months after the start of treatment, compared to 38% for local-regional failure patients (p less than 0.001). The incidence of distant metastases detected between the interval of 6 months to 2.5 years after treatment was significantly increased in patients with tumors of the oral cavity, oropharynx, supraglottic larynx, and glottis who developed local-regional failure within this time period, compared to those who remained locally controlled (19% distant metastases for local-regional failure vs 7% for local-regional control (p less than 0.001)). In contrast, there as no difference in the incidence of distant metastases in patients with carcinoma of the nasopharynx or hypopharynx regardless of the local-regional disease status. A Cox proportional hazards regression analysis demonstrated that local-regional control was the most significant variable affecting the development of distant metastases, followed by tumor site, N-stage, and T-stage. For all tumor sites, except for the hypopharynx and nasopharynx, improvements in local-regional control are likely to improve survival. Tumors of the hypopharynx and nasopharynx have a higher probability of micro-metastatic dissemination at the time of initial diagnosis, and until effective methods to treat disseminated disease are developed, the effect of local control on survival will not be readily discerned.

Review of the clinical results of fast neutron therapy

The clinical results reported from the different neutron therapy centres are reviewed. Fast neutrons were shown to be useful in the treatment of locally extended inoperable salivary gland tumours (average local control rates 67% for neutrons compared to 28% for photons). For paranasal sinuses and some tumours of the head and neck area, especially extended tumours with large fixed lymph nodes, neutrons could also be of interest. By contrast, the results obtained for brain tumours were, in general, disappointing. Neutrons were shown to be beneficial in the treatment of well differentiated soft tissue sarcomas, as well as to bone- and chondrosarcomas. For locally extended prostatic adenocarcinoma, a RTOG randomized trial gave local control rates of 77% for mixed schedule compared to 31% for photons. Neutrons could be useful also for palliative treatment of melanomas. Further studies are needed in order to evaluate the benefit of fast neutrons for other localizations such as uterine cervix, bladder and rectum. It can be concluded that fast neutrons could be of interest for about 10% of the radiotherapy patients, but it is likely that the new high-energy hospital-based cyclotrons will further extend the indications of neutron therapy. However, patient selection remains one of the main problems and there is a need for development of individual predictive tests.

Mixed neutron/photon irradiation of unresectable squamous cell carcinomas of the head and neck: the final report of a randomized cooperative trial

Three hundred and twenty-seven patients with inoperable squamous cell carcinomas of the head and neck were entered on a randomized study comparing a mixture of neutron and photon ("mixed beam") radiation therapy with photon/electron radiation therapy. Neutron treatment was delivered with fixed-beam, physics-laboratory-based equipment. Patients with histologically proven tumors of T-stage T2, T3, or T4 and any N-stage were eligible for randomization. Primary tumor sites were limited to cancers originating in the oral cavity, oropharynx, supraglottic larynx, or hypopharynx. Patients entered on this study now have a minimum at-risk follow-up period of 6 years. Study results reveal no significant differences in overall loco-regional tumor control rates or survival. Subgroup analysis reveals significant differences based on whether or not patients presented with positive lymph nodes. Loco-regional tumor control rates for patients presenting with positive lymph nodes were 30% for mixed-beam-treated patients versus 18% for photon-treated patients (p = 0.05). Loco-regional tumor control rates for patients presenting without positive lymph nodes were 64% for photon-treated patients and 33% for mixed-beam-treated patients (p = 0.004). Control of tumor located in the nodal sites favored mixed beam over photons by a margin of 45% (49/109) to 26% (23/87) with a significance of p = 0.004. Possible explanations for these contradictory findings are discussed.

Nasopharyngeal carcinoma in Saudi Arabia: a retrospective study of 166 cases treated with curative intent

A retrospective review was performed of the medical records of 166 adult patients with biopsy-proven carcinomas of the nasopharynx treated with curative intent at King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia. All patients were treated between June 1975 and December 1985 using megavoltage therapy equipment. Most patients presented with advanced nodal disease: 23 patients (13.9%) were N0, 16 patients (9.6%) were N1, 29 patients (17.5%) were N2, and 98 patients (59%) were N3. The overwhelming majority of patients had nonkeratinizing lesions (158/166). At the time of analysis, mean follow-up time was 24.2 months (range 2-108). Actuarial curves are presented for local/regional control as a function of T-stage and N-stage and for survival and time to development of distant metastases as a function of N-stage. At 4 years local/regional control was 70% for T1 lesions, 59% for T2 lesions, 30% for T3 lesions, and 35% for T4 lesions. There was little correlation between local/regional control and N-stage being about 50% at 4 years for all nodal subgroups. Only six patients exhibited an isolated first failure in the regional nodes alone, whereas 60 patients failed initially at the primary site (either alone or in conjunction with a simultaneous nodal failure). The development of distant metastases correlated to some extent with nodal disease ranging from 20% at 4 years for T1/T2 N0 patients to 70% for patients who initially presented with N3 disease. Survival data was more difficult to obtain due to cultural biases in a medically unsophisticated patient population. True survival curves are bounded by calculating actuarial curves in two ways: death as the failure endpoint and death plus lost-with-active-disease as failure endpoints. In terms of the latter curves, at 4 years "survival" ranged from 39% for patients with T1/T2 N0 lesions to 23% for patients with N3 lesions.

Radical radiation alone versus radical radiation plus microwave hyperthermia for N3 (TNM-UICC) neck nodes: a prospective randomized clinical trial

Between September 1985 and December 1986, 44 N3 (TNM-UICC) metastatic squamous cell cervical lymph-nodes were randomized to receive conventionally fractionated radical irradiation (RT) to a total dose of 64-70 Gy, or conventionally fractionated radical irradiation plus twice a week local microwave hyperthermia (Ht). The two major end points of this study were (a) local control rates evaluated at 3 months after the end of combined therapy and (b) incidence of acute local toxicity. Thirty-six nodes (82%) were evaluable as of December 1986, at which time there was a premature closure of this study due to ethical reasons. An interim analysis had revealed a statistically significant difference in complete response rates in favor of the combined arm (p = 0.0152). The complete response rates were 82.3% (14/17) for the combined treatment arm versus 36.8% (7/19) for the control irradiation arm, leading to an iso-dose thermal enhancement ratio (TER) value of 2.23. Both arms are comparable in average total RT dose delivered (RT: 67.05 Gy; RT + Ht: 67.85 Gy) and in average maximum node diameter (RT arm: 4.81 cm; RT + Ht: 4.88 cm). Acute local toxicities were similar in irradiated and heated plus irradiated neck regions; only one skin burn was observed. As possible treatment related death, one patient in the RT + Ht arm died 2 months after completion of therapy with a carotid rupture associated with extensive tumor necrosis. These results confirm previous non-randomized reports suggesting that hyperthermia in combination with full dose conventionally fractionated irradiation significantly enhances the chance of early local control of fixed N3 neck nodes without exhibiting an increase of acute local toxicity.

A comparison of clinical and laboratory data on neutron therapy for locally advanced tumors

Experimental results suggest advantages for neutrons where cells are hypoxic, in tumors which are slowly growing and also in a relative sparing of bone damage. The neutrons available at Hammersmith were of 7.5 MeV energy and produced a poorly penetrating beam, unsuitable for treating tumors in the pelvis and abdomen. Patients with locally advanced tumors in superficial sites were therefore selected to assess the effects of neutrons on normal and malignant tissues. One hundred and eight-nine patients had between them 191 locally advanced (T4 N0-3) tumors in the oral cavity, paranasal sinuses, salivary glands, and breast. Neutron therapy resulted in complete regression in 84% of which 13% subsequently recurred. Median survival for the whole group was 32 months. Twenty-eight other patients had advanced tumors of the head and neck which were recurrent after X ray therapy and other treatments; 82% of these completely regressed for more than 1 year. Complications appeared in 27% of patients not previously treated and in 46% who had already undergone X ray therapy. Seventy-four per cent of complications started in the skin. With neutrons of this energy there is minimal sparing of the skin and uneven distribution of dose resulting in "hot" spots. These affected skin, subcutis, and muscle. The high rates of control in these large tumors, the low incidence of bone necrosis, and the repair of some bones eroded by tumor correlate well with the experimental data. There was rapid regression of the tumor and close correlation between early and late effects on skin and subcutis. These two observations may relate to the fractionation, total dose, and overall time of treatment of 1560 cGy neutron dose given in 12 fractions over 28 days.

An evaluation of fast neutron irradiation in the treatment of squamous cell carcinoma in cervical lymph nodes

Analyses have been made of the response of metastatic cervical lymph nodes following neutron therapy, either as part of a randomized trial or in patients treated electively. In the trial patients, the overall regression and local control rates were similar after photons and neutrons. Mobile nodes, less than 3.0 cm, appeared to respond better to neutron therapy, and node masses greater than 3.0 cm had better control after photon therapy. The differences observed however were not statistically significant. There was a highly significant association between the control of the primary tumor and control of nodal disease. No survival advantage for neutrons was observed in association with apparently better control rates in cervical nodes.

Fast neutron therapy for squamous cell carcinoma in the head and neck region: results of a randomized trial

A randomized trial of fast neuron therapy compared with 4MV photons for patients with head and neck cancer is reported. One hundred and sixty-eight patients were recruited between 1977 and 1984. The minimum follow-up is 2 years. Three patients were withdrawn before treatment began. Eighty-five were allocated to neutron therapy and 80 to receive photon therapy. All patients had squamous cell cancers in one of four primary sites: oral cavity, oropharynx, larynx, and hypopharynx. Local tumor control was similar in both groups: 44.7% after neutrons and 45.0% after photons. Salvage surgery was performed on 18 patients in each treatment group for residual or recurrent cancer. Acute radiation reactions of the mucous membranes were significantly more severe after photons. The number of patients with serious late reactions was greater after neutron therapy but the difference was not statistically significant. There were six deaths related to late morbidity after neutron therapy but none after photon therapy. Survival was better after photon therapy but the difference compared with the neutron group failed to reach statistical significance. When intercurrent deaths are excluded, the difference is less marked. Photon therapy was clearly better in terms of disease-free survival giving a 2-year local disease-free rate of 41.3% (s.e. 5.5%) compared with 29.4% (s.e. 4.9%) after neutrons.

The Amsterdam fast neutron therapy project: a final report

In the period from February 1975 through September 1981 a total of 435 patients received radiotherapy with the 14 MeV d + T neutron generator, hospital based in the Netherlands Cancer Institute (the Antoni van Leeuwenhoek Hospital). Preliminary data on clinical results were published during the past few years. In this paper a final report is given of the program. The results can be summarized as follows: The neutron generator fulfilled the criteria for clinical use, that is it was reliable and had the required minimal output of 10(12) neutrons s-1. However, the dose distribution was more comparable with a 250 kV X-ray machine than with a modern accelerator. A number of physical parameters of importance for clinical neutron dosimetry have been determined for our therapy unit. These data, as well as the results of dosimetry intercomparisons in which our institute participated, contributed in the drafting of a European protocol for clinical neutron dosimetry. Pilot studies were carried out on different tumor sites, including head and neck, brain, pelvis, soft tissue and pulmonary metastases. In many patients local tumor control was seen, however, often concomitant with severe complications, especially in deep seated tumors. Randomized clinical trials were carried out for head and neck tumors (in collaboration with some other European centers) and for inoperable bladder and rectal tumors. No significant difference was observed in local tumor control or late morbidity between photon and neutron irradiation for the head and neck tumors. Also the results for pelvic tumors failed to demonstrate an advantage for neutron therapy. In this study two neutron arms were used with different dose schedules. As could be expected a higher local control rate was noticed for the higher neutron dose group, but concomitant with a higher complication rate. From our experience we have to conclude that treatment with our fast neutron treatment facility did not result in a benefit over photon irradiation. It seemed that the differential effect between tumor and normal tissues is smaller with fast neutrons than with photons.

Particle radiation therapy

Current interest in attempting to identify any therapeutic advantages of beams of heavy particles (heavier than electrons) over photons is based on differences in physical absorption and radiobiologic interactions. The article discusses: dose distributions in tissue, which are markedly different for particles than for high energy photons and so may be clinically advantageous for the former; differences in radiobiologic responses, which could lead to increased tumor cell killing and a possible increase in the therapeutic ratio for particles; clinical experience to date; directions for and impediments to future research.

Clinical evaluation of neutron beam therapy. Current results and prospects, 1983

Some 9000 patients throughout the world have been treated by some form of neutron beam therapy. These include patients with advanced nonresectable tumors in many different sites treated with a variety of neutron beam generators varying widely in beam energy. Protocols were largely nonrandomized and included both mixed beam studies (neutrons + photons) and neutrons alone in varying doses. In spite of wide variation in equipment, treatment technique, and philosophy, some consistent trends have been identified: (1) in general, the neutron results have been at least as good as those of the photon controls measured in terms of local control, although the incidence of significant side effects have been higher; (2) in none of the randomized studies conducted so far, largely comprising epidermoid carcinomas of the head and neck, has a clear survival advantage for neutrons over photon controls been demonstrated at a statistically significant level; (3) results with mixed beam studies have been uniformly equivocal, with marginally significant differences in favor of the experimental groups compared with the photon controls; (4) adenocarcinomas of the gastrointestinal tract (GI) tract, including tumors of the salivary gland, pancreas, stomach, and bowel, appear to be responsive to high linear energy transfer (LET) radiation; (5) nonepidermoid, radioresistant tumors (sarcoma of bone and soft tissue and melanoma) yield a consistantly high local control rate, with neutron irradiation strikingly superior to those reported with photon therapy; and (6) in the central nervous system, both normal tissues and tumors appear to be exceptionally sensitive to neutron irradiation, therapeutic ratios are small, and the prospect of cure remains remote. It is concluded that neutrons are efficacious for certain specific tumor types, but that essentially new study designs, based on nonrandomized matched case comparisons, will be required to prove the merit of the new modality.

Mixed beam radiation therapy for unresectable squamous cell carcinomas of the head and neck: the results of a randomized RTOG study

Three hundred and twenty-two patients with inoperable squamous cell carcinomas of the head and neck were entered on a randomized study comparing "mixed beam" radiation therapy with photon radiation therapy. Patients with histologically proven tumors of T-stage T2, T3, or T4 and any N-stage originating in the oral cavity, oropharynx, supraglottic larynx, or hypopharynx were eligible. One hundred forty-five patients were randomized to photon treatment and 177 were randomized to mixed beam treatment. No significant differences could be demonstrated between the experimental and control groups for primary tumor control or overall survival, although there was an advantage for mixed beam treatment over photon treatment for patients with metastatic cervical adenopathy (69 vs. 55% complete response rate in the nodes, p = .024). It is concluded that mixed beam radiation therapy does not offer a significant advantage over photon radiation therapy for patients with advanced squamous cell carcinomas of the head and neck.

Current status of high linear energy transfer irradiation

Based on laboratory investigations, high linear energy transfer (LET) particle irradiation is capable of more efficient cell kill than that associated with conventional or low LET irradiation. The advantages of high LET irradiation include: (1) a greater ability to damage hypoxic cells; (2) a lesser ability for repair of sublethal and potentially lethal radiation-induced damage; (3) less variation in radiation sensitivity relative to the cell cycle; and (4) a greater ability to deposit the radiation dose in the region of the tumor as opposed to the normal surrounding tissue (neutrons do not have this advantage compared to other particle therapy). Despite these laboratory advantages, it has been difficult to demonstrate any advantage of high LET irradiation in the clinic. A number of new developments have occurred to test the role of high LET: (1) sophisticated technology to enable treatment delivery with higher dose rate and improved depth dose; (2) the construction of hospital-based facilities; and (3) the development of randomized studies involving diseases in which the risk of early metastasis is minimized. It is hoped that careful study in the clinic over the next decade will elucidate the role of high LET particle therapy.

The interaction between X-rays and 3 MeV neutrons in the skin of the mouse foot

Mouse feet were irradiated with mixtures of 3 MeV neutrons and 140 kVp X-rays given simultaneously or within 24 hours of each other. The effects of different treatments were contrasted by comparing the doses required to give equal skin reactions. Irradiation was given as 1, 2, 4 or 8 equal fractions, in order to assess r.b.e. and the shapes of the underlying dose-response curves for mixed beams over a wide range of dose per fraction. All dose-effect curves were well fitted by a linear-quadratic (alpha, beta) model. For X-rays and neutrons given simultaneously, the linear coefficient (alpha) decreased by a factor of 4.80 while the quadratic coefficient (beta) increased by a factor of only 1.44 when the proton contamination in the beam increased from 11 to 100 per cent, with alpha/beta changing from 95.0 to 13.8. The data from simultaneous X-ray and neutron irradiation were consistent with full interaction of those effects from the two radiations which give rise to the total quadratic component of effect. When the two radiations are separated by up to 24 h, this interaction decreases but does not entirely disappear.

Response of epidermoid and non-epidermoid cancers of the head and neck to fast neutron irradiation: the Fermilab experience

One hundred and six patients with locally advanced cancers of the head and neck were treated with neutrons at the Fermilab Neutron Therapy Facility. Of these, 44 patients were previously untreated, 33 were recurrent following attempted surgery and 29 patients had previously received a full course of radiation therapy with conventional radiation. Results were analyzed to study the influence of stage, previous management, site of origin and tumor histology on local control of the disease. The most significant factor determining the outcome in this series of patients is the histological type. For epidermoid carcinoma, long term local control was achieved in 17/35 patients (49%) in the previously unirradiated group. With non-epidermoid tumors (adenocarcinoma, cylindroma, muco-epidermoid carcinoma), the local control rate was 28/39 (72%). Disease-free survival analysis also shows a survival advantage in non-epidermoid lesions treated with neutrons. It is concluded that neutron beam therapy may probably be the treatment of choice for non-resectable or recurrent non-epidermoid cancers of the head and neck and requires a clinical trial to establish this observation.